Aluminoxane process and product

ABSTRACT

An aluminoxane product is prepared by reacting water which contains a stabilizing agent, such as a lithium halide, with a hydrocarbyl aluminum compound, such as tri-methylaluminum, in an organic solvent. The product has increased resistance to gel-formation therein because of the stabilizing agent dissolved in the water used in forming the reaction product.

REFERENCE TO RELATED APPLICATION

This application is a division of our prior co-pending application Ser.No. 08/556,479, filed Nov. 13, 1995, now U.S. Pat. No. 5,693,838, issuedDec. 2, 1997.

DESCRIPTION

This invention relates generally to the preparation of aluminoxanes(also known as alumoxanes) and more particularly to the preparation ofhydrocarbylaluminoxanes, such as methylaluminoxane, by reacting ahydrocarbyl aluminum compound with water which contains a stabilizingagent, such as a metal salt, which solution is dispersed in an organicsolvent.

Vandenberg, U.S. Pat. No. 3,219,591 reported the catalytic activity ofcompounds formed by the reaction of trialkyl aluminum with limitedamounts of water in the polymerization of epichlorohydrin and otheroxiranes. Shortly thereafter, Manyik, et al. U.S. Pat. No. 3,242,099reported the use of aluminoxanes, made by reacting 0.85-1.05 moles ofwater with hydrocarbyl aluminum compounds such as triisobutylaluminum,as co-catalysts with certain transition metal compounds in thepolymerization of mono-unsaturated alpha-olefins; e.g. ethylene andpropylene. Isobutylaluminoxane was also made by adding an equal molequantity of water to a heptane solution of triisobutylaluminum.

Manyik, et al. U.S. Pat. No. 3,300,458 prepared alkylaluminoxane bypassing a hydrocarbon through water to form a wet hydrocarbon and mixingthe wet hydrocarbon and an alkyl aluminum/hydrocarbon solution in aconduit.

Schoenthal, et al. U.S. Pat. No. 4,730,071 show the preparation ofmethylaluminoxane by dispersing water in toluene using an ultrasonicbath to cause the dispersion and then adding a toluene solution oftrimethylaluminum to the dispersion. Schoenthal, et al. U.S. Pat. No.4,730,072 is similar except it uses a high speed, high shear-inducingimpeller to form the water dispersion.

Edwards, et al. U.S. Pat. No. 4,722,736 describe an aluminoxane processin which water is introduced below the surface of a solution ofhydrocarbyl aluminum adjacent to a stirrer which serves to immediatelydisperse the water in the hydrocarbon solution.

A problem associated with free water addition to trialkylaluminum toproduce aluminoxane solutions in organic solvents is that the solutionsmay produce gel and/or small particles which aggregate to form gel onstanding. Even when the particles and/or gel are removed by filtration,additional gel can form in the solution after 2 or 3 weeks, especiallywhen originally-prepared dilute solutions are concentrated to containhigher aluminoxane contents which are convenient for storage, shipmentand use.

Sangokoya, U.S. Pat. No. 5,157,137 describes a process for treating MAOwith an anhydrous salt and/or hydroxide of an alkali or alkaline earthmetal to inhibit gel and gel forming compounds.

We have now discovered a process for making aluminoxanes by free wateraddition which provides unique, gel free, stable products.

In accordance with this invention there is provided a process for makingan aluminoxane, said process comprising reacting water which contains astabilizing agent with a hydrocarbyl aluminum compound in an organicsolvent so as to produce an aluminoxane product.

Also provided is a new stable aluminoxane product prepared by this novelprocess.

Hydrocarbylaluminoxanes may exist in the form of linear, cyclic, cagedor polymeric structures with the simplest compounds being atetraalkylaluminoxane such as tetramethylaluminoxane, (CH₃)₂AlOAl(CH₃)₂, or tetraethylaluminoxane, (C₂ H₅)₂ AlOAl (C₂ H₅)₂. Thecompounds preferred for use in olefin polymerization catalysts usuallycontain about 4 to 20 of the repeating units: ##STR1## where R is C₁ -C₈alkyl and is preferably methyl. The exact structure of aluminoxanes hasnot been defined and they may contain linear, cyclic, caged and/orcross-linked species. Methylaluminoxanes (MAOs) normally have lowersolubility in organic solvents than higher alkylaluminoxanes and themethylaluminoxane solutions tend to be cloudy or gelatinous due to theseparation of particles and agglomerates. In order to improve thesolubility of the methylaluminoxane, higher alkyl groups, e.g. C₂ toC₂₀, can be included such as by hydrolyzing a mixture oftrimethylaluminum with a C₂ to C₂₀ alkylaluminum compound such as, forexample, triethylaluminum, tri-n-propylaluminum, triisobutylaluminum,tri-n-hexylaluminum, tri-n-octylaluminum or a triarylaluminum. Suchmixed methyl higher alkyl or aryl aluminoxanes are included in the term"methylaluminoxane" as used herein.

Any hydrocarbyl aluminum compound or mixture of compounds capable ofreacting with water to form an aluminoxane can be used. This includes,for example, trialkylaluminum, triarylaluminum, mixed alkyl-arylaluminum, and the like.

The preferred hydrocarbyl aluminum compounds are the alkyl aluminumcompounds, especially trialkylaluminum compounds such astrimethylaluminum, triethylaluminum, triisobutylaluminum,tri-n-hexylaluminum, trioctylaluminum and the like. Of these, the morepreferred are the tri-C₁₋₄ -alkylaluminum compounds.

Of the various hydrocarbyl aluminoxanes, methylaluminoxane andethylaluminoxane are the more difficult to prepare because of theextreme reactivity of trimethyl aluminum and triethylaluminum withwater. The most reactive is trimethylaluminum and, accordingly, thepreferred use of the process of the invention is to makemethylaluminoxane.

The reaction is carried out in an inert solvent. Any inert solvent canbe used. The preferred solvents are aliphatic and aromatic hydrocarbons.Aromatic hydrocarbons are more preferred such as toluene, xylene,ethylbenzene, cumene, mesitylene and the like. The most preferredsolvent is toluene.

The concentration of the hydrocarbyl aluminum compounds in the inertsolvent can range from about 1-30 weight percent. A preferredconcentration is about 5-10 weight percent, more preferably 10-15 weightpercent.

The stabilizing agents are combined with the water used to hydrolyze thehydrocarbyl aluminum compounds. The term "stabilizing agent" as usedherein includes any water soluble inorganic compound which is effectiveto provide alkylaluminoxanes having improved solubility in organicsolvents when added to the water used to hydrolyze the hydrocarbylaluminum compound. Preferred are water soluble (at least 1 gram/100 mLH₂ O at 25° C.) metal salts and their ammonium analogs and especiallyalkali and alkaline earth metal halides. Non-limiting examples of suchcompounds include, NaBr, NaF, NaCl, LiCl, LiBr, LiF, LiI, KCl, MgCl₂,MgI₂, and the like. Halide salts of other metals as well as ammonium andmetal nitrates, nitrites, sulfates, sulfites, phosphates, phosphites,borates, and carbonates can be used, for example Na₂ SO₄, LiBO₂, LiCO₃,LiNO₂, Li₂ SO₄, MgSO₄, NaNO₃, NaNO₂, NaPO₃, Na₂ SO₃, Al₂ (SO₄)₃ Na₃ PO₄,and the like. Hydroxides such as LiOH, Ba(OH)₂, KOH, CsOH, NaOH can alsobe used.

The stabilizing agents are added to make from about 0.05 percent byweight up to saturated solutions in water. Preferably from about 0.1 to50 percent by weight aqueous solutions of stabilizing agents are used tohydrolyze the hydrocarbyl aluminum compounds.

The stabilizing agent containing aqueous solutions can be combined withthe hydrocarbyl aluminum compound in an inert organic solvent by anysuitable manner such as the various ways which are known in the art. Forexample, the process which is described in U.S. Pat. No. 4,908,463 wherewater dispersed in an organic solvent is mixed with a solution of thehydrocarbyl aluminum in a "T-shaped" reactor. The amount of waterdispersed in the solvent is preferably from about 0.25 to 5.0 weightpercent, based on the weight of solvent. A more preferred amount isabout 0.5 to 3.0 weight percent and most preferred is about 1.0 to 2.5weight percent. The reactants are combined in proportions to providefrom about 0.5 to 4.0 moles of hydrocarbyl aluminum compound per mole ofwater and from about 5.0 to 10,000 moles of hydrocarbyl aluminumcompound per mole of stabilizing agent and, preferably, from about 50 to5,000 moles of hydrocarbyl aluminum compound per mole of stabilizingagent.

The invention is further illustrated by, but is not intended to belimited to, the following examples.

EXAMPLE 1

An aqueous LiCl solution was prepared which contained 0.35 pounds (158.9grams) of anhydrous LiCl salt in 3 gallons (11.36 liters) of solution.This salt solution was fed into a flow-through sonicating horn at a rateof 0.15 lbs. (68.1 gms) per hour and emulsified with toluene fed at arate of 10 pounds (4.54 Kg) per hour. This emulsion was then reactedwith a 12 weight percent trimethylaluminum (TMA) in toluene stream fedat a rate of 11 pounds (5.38 Kg) per hour. The TMA-to-water mol ratiowas 2.2 to 1. The reaction mixture was then discharged into an eductor,mixed with methylaluminoxane (MAO) product solution from a pump-aroundloop, and finally discharged into the vapor space of a degassing vessel.The toluene feed to the sonication horn was maintained at a temperatureof -2° C. The TMA feed stream was maintained at a temperature of 5° C.The degassing vessel was maintained at a temperature of 20° C.

The crude product was sampled and it was noticed that there waspractically no degassing in the sample. This behavior is very differentfrom that observed for samples of crude MAO prepared using plain water.Normally crude MAO will continue to degas for 3 to 4 hours aftersampling. The solids formed in the new MAO product also appear to settlefaster than the solids in normal MAO crude.

A sample of the new MAO was taken from the product stream during the runand was filtered. The solids produced from the reaction appear to filtereasier than those formed by the standard MAO plain-water process. Thefiltered crude was then batch flashed to concentrate the product. Thecrude product was concentrated by flashing of the solvent using a 104°C. wall temperature, a 60° C. bulk temperature, and a vacuum of 100 mmHg. The resulting solution was 8.86 weight percent Al. The TMA contentof the solution was 4.84 weight percent TMA. The sample contained lessthan 20 ppm Cl. The aluminum content equates to a 15 weight percentsolution of MAO. This 15 weight percent MAO solution was isolated fromthe flash pot as a clear liquid.

The increased stability of the new MAO was demonstrated by placing a 15weight percent solution in an oven at 60° C. for 4 days, along with a 30weight percent solution of conventional plain-water prepared MAO. Afterthe 4 days the MAO was cloudy, but the new MAO was still clear. The oventemperature was then increased to 65° C. for two more days. The new MAOremained clear. The oven temperature was then raised to 80° C. After oneday at 80° C. the new MAO was still clear, but regular MAO wascompletely gelled.

After the oven test, the 15 weight percent MAO solution was used in apolymerization test to determine if it was active as a co-catalyst.Three mL of the 15 weight percent MAO solution were added to 100 mL oftoluene. To this solution, 0.25 mL of a solution of 18 mg of zirconocenedichloride--(C₅ H₅)₂ ZrCl₂ --dissolved in 18 mL toluene was added. Thesolution was stirred and heated in an oil bath to 80° C. A constantpressure of ethylene (60 psig) gas was then placed on the reactionvessel. After 35 minutes, the vessel was removed from the oil bath andthe pressure was released. The polyethylene product was collected byfiltration, washed and dried. The final yield was 7.05 grams ofpolyethylene.

The polymerization test was repeated with standard plain-water preparedMAO. A change was made in the volume of MAO solution added based on thecalculated weight percent MAO. Two mL of 23 weight percent MAO was addedto 100 mL of toluene and then 0.25 mL of the zirconcene dichloridetoluene solution was added. The reaction was performed under the sameconditions for the same length of time as the above polymerization test.The polyethylene was collected, washed and dried. The final yield was7.88 grams. Allowing for experimental error, this result equates toapproximately the same degree of reactivity as the new MAO which hasbeen heat aged. This demonstrates that the improved stability of the MAOprepared in accordance with the process of the invention is achievedwithout loss of activity.

EXAMPLE 2

MAO was prepared using the same LiCl salt solution as in Example 1, butthe feed rates and temperatures were somewhat different.

The salt solution was fed at a rate of 0.16 lbs (72.6 gms)/hr. Thetoluene stream was fed at 11.6 lbs (5.26 Kg)/hr. The TMA stream was fedat 11.6 lbs (5.26 Kg)/hr. These feed rates produced a TMA-to-water moleratio of 2.22 to 1. The temperature of degassing vessel for the secondrun was maintained at 10° C. The other feed temperatures were maintainedthe same as in Example 1.

A sample of the MAO was taken from the second run and was filtered andflashed under the same conditions as the first run sample of Example 1.The final weight percent Al of this sample was 11.4. The samplecontained 7.96 weight percent TMA and 0.01 weight percent Cl. Theseresults equate to an 18 weight percent MAO solution. This solution wasclear upon leaving the flash pot. A portion of the sample was placed inan oven at 65° C. for two days and it remained clear and gel free. Theoven was then increased to 80° C., and a sample of standard 10 weightpercent MAO was placed in the oven. After one day the new MAO was stillclear, but the 10 weight percent MAO began turning cloudy.

The solids filtered from the sample from Example 2 were analyzed. Thesolids contained 11.5 weight percent Al, no detectable TMA, 0.35 weightpercent Cl, and a gas/Al mole ratio of 1.47. This ratio is approximatelyequivalent to that of standard plain-water prepared MAO. These resultsindicate that these solids could be a higher molecular weight MAO. Anexperiment was conducted to determine if the solids could be used asboth an activator and a support for a metallocene catalyst. The solidwas rinsed from the bottle with toluene and collected on a coarse frit.The solids were then washed with isopentane and a fine white powderresulted. The solid was removed from the frit and slurried with toluene.Six mL of a 0.100 gram of zirconocene dichloride dissolved in 60 mLtoluene solution was then added to the slurry and the resulting mixtureagitated. The slurry began changing color from white to peach colored.After approximately one-half hour, the slurry was transferred to thecoarse frit for filtering. The toluene was filtered from the solid. Thepeach-colored solid was then rinsed with isopentane. Upon rinsing, thesolid turned to a white powder. One-half gram of this solid was placedinto a reaction vessel and 25 mL of toluene was added to produce aslurry. The vessel was then placed in an oil bath at 80° C. and theslurry was stirred at this temperature. Ethylene was applied to thevessel at a continuous pressure of 60 psig while being maintained at 80°C. After 10 minutes, the vessel was removed from the oil bath and thepressure on the vessel was released. The polyethylene produced from thisreaction was washed, filtered, and dried. The final yield ofpolyethylene was 2.1 grams.

What is claimed is as follows:
 1. An aluminoxane comprising the reactionproduct of (A) free, liquid water which has a stabilizing agentdissolved therein, and (B) a hydrocarbyl aluminum compound, saidreaction product having increased resistance to gel-formation thereinbecause of the stabilizing agent dissolved in the free, liquid waterused in forming said reaction product.
 2. The product of claim 1 whereinthe stabilizing agent dissolved in the free, liquid water is selectedfrom the group consisting of metal salts and their ammonium analogs,including mixtures thereof.
 3. The product of claim 1 wherein thestabilizing agent dissolved in the free, liquid water is at least onealkali metal salt or at least one alkaline earth metal salt.
 4. Theproduct of claim 1 wherein the stabilizing agent dissolved in the free,liquid water is a lithium halide.
 5. The product of claim 1 wherein thehydrocarbyl aluminum compound is a trialkylaluminum.
 6. The product ofclaim 5 wherein the stabilizing agent dissolved in the free, liquidwater is selected from the group consisting of metal salts and theirammonium analogs, including mixtures thereof.
 7. The product of claim 5wherein the stabilizing agent dissolved in the free, liquid water is atleast one alkali metal salt or at least one alkaline earth metal salt.8. The product of claim 5 wherein the stabilizing agent dissolved in thefree, liquid water is a lithium halide.
 9. The product of claim 5wherein the trialkylaluminum is trimethylaluminum.
 10. The product ofclaim 9 wherein the stabilizing agent dissolved in the free, liquidwater is selected from the group consisting of metal salts and theirammonium analogs, including mixtures thereof.
 11. The product of claim 9wherein the stabilizing agent dissolved in the free, liquid water is atleast one alkali metal salt or at least one alkaline earth metal salt.12. The product of claim 9 wherein the stabilizing agent dissolved inthe free, liquid water is a lithium halide.
 13. The product of claim 9wherein the stabilizing agent dissolved in the free, liquid water islithium chloride.
 14. The product of any of claims 1-13 wherein theproduct is dissolved in an organic solvent.
 15. A solution in an organicsolvent of an aluminoxane comprising the reaction product of (A) free,liquid water which has an aluminoxane gelation inhibitor dissolvedtherein, and (B) a hydrocarbyl aluminum compound, said solution beingcharacterized by remaining clear and gel-free longer than an identicalsolution made and stored in the same way except made without saidaluminoxane gelation inhibitor.
 16. A solution of claim 15 wherein thealuminoxane is a methylaluminoxane and wherein the organic solvent is ahydrocarbon solvent.
 17. A solution of claim 16 wherein the aluminoxanegelation inhibitor dissolved in the free, liquid water is a lithiumhalide.
 18. A solution of claim 16 wherein the aluminoxane gelationinhibitor dissolved in the free, liquid water is lithium chloride.
 19. Asolution of any of claims 15-18 wherein said reaction product is formedin situ in said organic solvent.